Re: New Member! New-old 1870s stone vernacular farmhouse
Posted: Sat Aug 15, 2015 9:01 pm
Lime plaster has become preservation-only in Europe too (and amazingly quickly, in the early 80s even young farmers would still slake their own lime in a pit and build their entire house with that lime and sand, only buying bricks from the store, heck, I watched the same farmers slake lime in that pit and whitewash the walls probably around 1995!) but I don't think any plasterer waits for 4 full weeks between coats, more like a few days and then 2 weeks from the finish coat until painting, unless whitewash is used, which is always applied to the still-wet plaster as soon as it's become solid enough not to be marred by the brush.
The real disadvantage of gypsum in old houses seems to be that it isn't moisture-resistant at all so it fails quickly when the walls get even a little damp. Stone walls tend to have few problems with rising damp but they do occasionally get condensation issues in humid summers. For a perfectly smooth finish a mix of lime putty and fine marble dust is used but that's really rare even here. We had to live with a somewhat rough finish coat, the whitewash smoothed that out to some extent anyway and future coats will eventually make the plaster perfectly smooth.
The real disadvantage of gypsum in old houses seems to be that it isn't moisture-resistant at all so it fails quickly when the walls get even a little damp. Stone walls tend to have few problems with rising damp but they do occasionally get condensation issues in humid summers. For a perfectly smooth finish a mix of lime putty and fine marble dust is used but that's really rare even here. We had to live with a somewhat rough finish coat, the whitewash smoothed that out to some extent anyway and future coats will eventually make the plaster perfectly smooth.